1. Field of the Invention
The present invention relates to automatic controlled parachute systems. More particularly, it relates to a pneumatic actuator system for controlling riser webs and weight distribution for remote or autonomous control of parachute flight.
2. Discussion of Related Art
Parachutes have evolved over the years into highly sophisticated systems, and often include features that improve the safety, maneuverability, and overall reliability of the parachutes. Initially, parachutes included a round canopy. A skydiver was connected to the canopy via a harness/container to suspension lines disposed around the periphery of the canopy. Such parachutes severely lacked control. The user was driven about by winds with little mechanism for altering direction. Furthermore, such parachutes had a single descent rate based upon the size of the canopy and the weight of the parachutist.
In the mid-1960""s the parasol canopy was invented. Since then, variations of the parasol canopy have replaced round canopies for most applications, particularly for aeronautics and the sport industry. The parasol canopy, also known as a gliding or ram air parachute, is formed of two layers of materialxe2x80x94a top skin and a bottom skin. The skins may have different shapes but are commonly rectangular or elliptical. The two layers are separated by vertical ribs to form cells. The top and bottom skins are separated at the lower front of the canopy to form inlets. During descent, air enters the cells of the canopy through the inlets. The vertical ribs are shaped to maintain the canopy in the form of an airfoil when filled with air. Suspensions lines are attached along at least some of the ribs to maintain the orientation of the canopy relative to the pilot. The canopy of the ram air parachute functions as a wing to provide lift and forward motion. Guidelines operated by the user allow deformation of the canopy to control direction and speed. Ram air parachutes have a high degree of lift and maneuverability.
Despite the increased lift from a ram air parachute, round canopies are still used for cargo drops. However, as the weight of cargo increases, the size of the canopy must increase to obtain an appropriate descent rate. Reasonable sizes of round parachutes greatly limit the amount of cargo which can be dropped. Therefore, a need exists for a parachute system which can carry additional cargo weight. Additionally, accurate placement of cargo drops from high altitude with round parachutes or unguided is impossible. Adjustments can be made for prevailing winds at various altitudes but the cargo is likely to be drift off course due to variations. Furthermore, improvements in surface-to-air missiles requires higher altitude drops in order to protect aircraft. In military use, round parachutes are generally used from an altitude around 1000 feet to ensure accurate placement. However, new, inexpensive, hand held surface-to-air missiles can put in jeopardy airplanes up to 25,000 feet in altitude. Current military technique is to use a special forces soldier to pilot both parachute and cargo to the ground from altitudes of 25-35,000 feet. This limits cargo to 650 pounds, as it must be attached to a human. Therefore, a need exists for an autonomous guided parachute system for cargo which can operate at high altitudes as well as scale to heavier cargo weights.
Parachute systems, either manned or automatic can be controlled in two different manners. These two manners may be used on round parachutes with minimal control, but are very effective for control of ram air or gliding parachutes. In one manner, steering or brake lines are attached to part of the parachute. By pulling on the lines, the aerodynamics of the parachute are changed to control the flight direction of the parachute. Manned parachutes generally use this method of control. In the second manner, the weight distribution under the parachute is changed. Typically, the suspension lines from the parachute are attached together in quadrants front left and right, and back left and right. Each group of lines are attached to a riser. Risers are typically structural webbing. They attach a group of suspension lines to the harness of the parachute system. Often, the risers incorporate a quick release mechanism in order to separate the parachute from the harness in the case of malfunction. If one of the risers is pulled, the weight under the parachute is shifted in that direction, which induces a turn in that direction.
Automatically controlled parachute systems may be used for unmanned parachute flights. Such systems allow cargo to be accurately dropped. The automatically controlled parachute may function autonomously or may be remotely controlled by an operator. In an automatically controlled parachute system, sensors are used to determine the position and flight information of the parachute system. The system then determines necessary changes in the flight direction and controls the parachute to provide those direction changes. In known systems, the brake lines of the parachute are used to control the direction of flight. As noted above, in order to control direction, the brake lines have to be shortened or lengthened.
Various devices are known for moving the brake lines. Most common are electric servo motors. Alternatively, the electric servo motors may be used to change the length of the risers to provide a weight shift for direction control. However, servo motors are ideal for high altitude drops. The cold temperatures, about xe2x88x9250xc2x0 C. at 30,000 feet, limit the useable power from batteries for controlling the motors. Cold weather batteries have poor power density, necessitating large heavy packs to provide sufficient power. The use of dc motors and large battery packs greatly complicate a systems construction, operation and of critical importance cost.
Another system is described in U.S. patent application Ser. No. 10/315,466, filed Dec. 9, 2002 (xe2x80x9cthe ""466 patent applicationxe2x80x9d), assigned to the same assignee as the present invention and incorporated herein by reference. The ""466 patent application describes flight controller for an automatically controlled parachute. In this system, pneumatic actuators are attached to the steering lines to provide direction control. This system is useful for high altitude operations because of the limited electrical needs. The power to move the actuators is stored in the form of compressed gas, not electricity. The power density of the compressed dry air or nitrogen is very high and remains unchanged for the purpose and the temperature range to be used. However, the significant deflection required by the steering lines requires an actuator with a long stroke or pulley system.
Another system proposes the use of McKinney muscle to control the risers of a round parachute. The McKinney muscle consists of a pneumatic rubber tube with an overbraid of crisscrossing reinforcement. When the tube is pressurized, it increases in diameter and decreases in length. The length can shrink by approximately 20% between an empty and a full tube. The McKenney muscle is built directly into at least some of the risers. In order to allow sufficient shortening of the riser, the riser must be excessively long. While round parachutes can accommodate long risers, they are not easily incorporated in a ram air or gliding wing parachute. Also, as the tube approaches maximum pressurization, the actuation force drops off to zero. Again, while a round parachute may utilize such an actuation system, it is not useful for a gliding wing system. The generated force vs. stroke curve is opposite to that required for a riser turn on a ram air wing. Finally, a significant amount of air is necessary for to provide a full stroke. A large gas tank is necessary as the power source for the system. The additional weight and size of the gas tank makes use of the system impractical in many situations.
According to an aspect of an invention, an automatic controllable parachute system includes a parachute canopy, a flight controller, and risers connecting the suspension lines of the parachute canopy to the flight controller. The flight controller includes a system for determining a desired direction for flight. Pneumatic piston actuators are incorporated into the risers of the parachute canopy. The pneumatic actuators are operated by the flight controller to alter the length of the risers for providing a turn. According to an aspect of the invention, the flight controller includes solenoids for controlling the pneumatic actuators. An electrical signal is sent from the flight controller to the solenoid. The solenoid causes the pneumatic actuator to open or close. A tank of compressed gas is used as the power source for the actuators. According to another aspect of the invention, the pneumatic piston actuators are positioned between and attached to portions of the webbing of the risers. According to another aspect of the invention the pneumatic piston actuators are mounted in a box containing the guidance system and utilize flexible cables as the piston rod. Such piston cables are plastic coated to effect a proper seal and attach to the riser to provide for a turn when retracted. The use of flexible cables allows for greater design possibilities as the cables can flex and pack up with the risers into the parachute container prior to deployment.